The present invention relates to pharmaceutical compositions and methods for regulating abnormal cell proliferation. More particularly, the present invention relates to pharmaceutical compositions and methods of treating diseases which are associated with pathologically hyperproliferating cells, such as tumors/cancers.
Diseases associated with abnormal cell proliferation, comprise numerous diseases of major clinical and economic impact for which no satisfactory treatment methods are available. Such diseases comprise those associated with pathological cellular hyperproliferation—notably malignant diseases—as well as benign tumors, pre-cancers, hyperplasias, polyps, warts, growths and the like; and autoimmune diseases characterized by hyperproliferating clones of autoreactive lymphocytes. Diseases associated with abnormal proliferation also comprise those conversely associated with pathological cellular hypoproliferation such as degenerative disorders, Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis (ALS), retinitis pigmentosa, and osteoporosis. Natural senescence and undesirable senescence-related phenomena such as wrinkling can also be considered as being degenerative disorders associated with cellular hypoproliferation.
Colon cancer, which is also known as cancer of the large bowel and colorectal cancer, is second only to lung cancer as a cause of cancer death in the United States. Colorectal cancer is a common malignant condition that generally occurs in individuals 50 years of age or older; and the overall incidence rate of colon cancer has not changed substantially during the past 40 years (Harrison's Principles of Internal Medicine, 14/e, McGraw-Hill Companies, New York, 1998). In 1999, 129,400 new cases of colorectal cancer were estimated in the United States, resulting in 56,600 deaths therefrom. The cumulative lifetime risk for the disease is 1 in 20. The strongest risk factor for colon cancer is age, with the incidence rates rising from 10 per 100,000 at age 40-45 to 300 per 100,000 at age 75-80. Men are more likely to develop colon cancer than women; black Americans are more likely than white Americans to be diagnosed with colorectal cancer; and smokers, drinkers, sedentary, and obese persons are more likely to develop colon cancer. The treatment of colon cancer once diagnosis is made depends on the extent of the cancer's invasion of the colon tissue, lymph nodes, and metastasis to other organs such as the liver. Surgery is the primary treatment and results in cure in approximately 50 percent of patients. However, recurrence following surgery is a major problem and often is the ultimate cause of death.
Cancer of the uterine cervix is one of the most common malignancies in women and remains a significant public health problem throughout the world. In the United States alone, invasive cervical cancer accounts for approximately 19 percent of all gynecological cancers (Miller et al. (1993) in “Surveillance Epidemiology, and End Results Program cancer Statistics Review: 1973-1990”, NIH Pub. No. 93-2789, Bethesda, Md.: National Cancer Institute). For example, in 1996, it is estimated that there Were 14,700 newly diagnosed cases and 4900 deaths attributed to this disease (American Cancer Society, Cancer Facts & Figures 1996, Atlanta, Ga.: American Cancer Society, 1996). In many developing countries, where mass screening programs are not widely available, the clinical problem is more serious. Worldwide, the number of new cases is estimated to be 471,000 with a 4-year survival rate of 40 percent (Munoz et al. (1989) “Epidemiology of Cervical Cancer” in “Human Papillomavirus”, New York, Oxford Press, pp 9-39; and National Institutes of Health, Consensus Development Conference Statement on Cervical Cancer, Apr. 1-3, 1996).
There is therefore clearly a long-felt and urgent need. for novel, safe and effective pharmacological agents which can modulate cell proliferation so as to treat diseases associated with abnormal cellular proliferation, such as tumors, for example colon cancer and cervical cancer.
Standard chemotherapeutic agents employed for treating various types of malignancies notably include those which target and block mitosis, such as Vinca alkaloids such as vincristine, taxol and related compounds. Some of these drugs are also used in non-neoplastic conditions; for example, colchicine in familial Mediterranean fever and gout, vincristine in autoimmune thrombocytopenia, etc. Remarkably, although mitosis is a normal process shared by all proliferating cells, anti-mitotic drugs can have an excellent therapeutic ratio with relatively few harmful side effects. It appears that cancer cells have a unique sensitivity to anti-mitotic drugs. Therefore there is an extensive effort in developing other drugs that target proteins regulating mitosis. Some (e.g. UCN01) are currently in clinical trials (Jordan, M. A. and L. Wilson, 2004. Nat Rev Cancer 4: 253-65; Keen, N. and S. Taylor, 2004. Nat Rev Cancer 4: 927-36; Sikorska, A. et al., 2004. Clin Lab Haematol 26: 407-11; Cerquaglia, C. et al., 2005. Cliff Drug Targets Inflamm Allergy 4: 117-24; Fuse, E. et al., 2005. J Clin Pharmacol 45: 394-403).
The mitosis regulatory protein SIL is a protein which is tightly regulated during the cell cycle and whose expression is limited to proliferating cells. Its mRNA expression is higher in rapidly proliferating cells and tissues, and it decreases rapidly during terminal differentiation. Upon entrance of arrested G0 cells into the cell cycle SIL is induced in an immediate early fashion. The SIL protein accumulates, reaches peak levels in mitosis and then degrades upon entrance to the next cell cycle (Izraeli, S. et al., 1997. Cell Growth Differ 8: 1171-9).
The SIL gene [stem cell leukemia (SCL) interrupting locus, also termed as STIL (SCL/TAL1 interrupting locus)], located on chromosome 1, was cloned from the most common chromosomal rearrangement in T-cell acute lymphoblastic leukemia (ALL). In this rearrangement, the coding region of SIL is deleted and its promoter assumes control of a downstream gene, SCL. The resulting aberrant expression of SCL leads to the development of leukemia (Aplan, P. et al., 1991. Mol Cell Biol 11: 5462-9). The human SIL gene encodes a large cytosolic protein of 150 kilodaltons composed of 1287 amino acid residues that has been found to be highly conserved in the mouse and zebrafish (Collazo-Garcia, N. et al., 1995. Genomics 30: 506-513; Golling, G. et al., 2002. Nat Genet 31: 135-40). The importance of SIL to cell growth and differentiation was also shown in a knockout mouse, which carried a null mutation of the Sil gene (Izraeli, S. et al., 1999. Nature 399: 691-4). Mice lacking the gene, die at mid-gestation, they manifest striking developmental defects in the midline and left/right body axis, and the most anterior end of the developing brain is not separated, resulting in holoprosencephaly (cyclopia), with the rest of the neural tube being apoptotic. Left/right asymmetry axis is randomized. SIL is not absolutely required for survival of normal cells as mouse embryonic stem cells lacking SIL proliferate normally and grow teratomas in nude mice that are indistinguishable from those formed by normal embryonic stem cells (Izraeli, S. et al., 1999. Nature 399: 691-4). Detailed analysis of the SIL knockout mice and additional genetic experiments suggest that SIL is required for the response to Hedgehog signaling (Izraeli, S. et al., 1999. Nature 399: 691-4; Izraeli, S. et al., 2001. Genesis 31: 72-7). However, it is still unclear if SIL participates in the biochemical signaling cascade induced by stimulation by Hedgehog proteins.
The critical requirement of SIL for cell growth, proliferation and survival during embryonic development, and its regulation during the cell cycle prompted the hypothesis that SIL might have a role in tumorigenesis. SIL has been found by the present inventors, and others, to be ubiquitously expressed in cancer and to characterize tumors with increased mitotic fraction (Aplan, P. et al., 1991. Mol Cell Biol 11: 5462-9; Izraeli, S. et al., 1997. Cell Growth Differ 8: 1171-9; Erez, A. et al., 2004. Oncogene 23: 5371-7). SIL was shown to be expressed by RNA and protein analysis in multiple types of cancer cells (tissues and cell lines), the only exception being gliomas where the expression of SIL is low. In contrast, in primary normal tissues it is expressed mainly in bone marrow, thymus, and testis. In non dividing tissues SIL expression is extremely low (Izraeli, S. et al., 1997. Cell Growth Differ 8: 1171-9). Publicly available microarray data describes patterns of SIL expression (see, for example, http://expression.gnf.org/cgi-bin/index.cgi#Q). Examples of cancers in which SIL has been shown to be overexpressed include primary cells and cell lines of acute lymphoblastic leukemia (ALL), acute myeloid leukemias (AML), chronic myeloid leukemia (CML), Burkitt's lymphoma, non-Hodgkin's lymphoma. Other types of cancers in which SIL has been shown to be overexpressed include primary cells and cell lines of lung cancer (both small and non-small cell lung cancer), colon cancer, breast cancer, prostate cancer, melanoma, cervical cancer, liver cancer, and teratocarcinoma. Immunohistochemical staining experiments have revealed high expression of SIL in up to a third of specimens tested for each of multiple types of cancer. The pattern of SIL expression has been studied in detail in lung cancer. Tumors highly expressing SIL had a higher mitotic index and a higher expression of other mitotic regulators (Erez, A. et al., 2004. Oncogene 23: 5371-7). These findings and others suggest that SIL expression characterizes a subset of more aggressive tumors with a higher mitotic fraction, and have found SIL to be one of the predictive genes for metastatic disease in adenocarcinomas of different tissues (Ramaswamy, S. et al., 2003. Nat Genet 33: 49-54). SIL protein expression correlates with the expression of mitotic checkpoint genes and with the mitotic index of the tumors, in itself a bad prognostic sign. Thus, overexpression of SIL is common in cancers and is associated with increased mitotic index, metastatic spread and consequently worse prognosis.
While, as described above, prior art anti-mitotic drugs can be used for treatment of diseases associated with pathological cellular hyperproliferation, such as cancer, such drugs nevertheless remain of limited effectiveness and are associated with harmful side-effects, for example towards healthy cells as a result of systemic drug administration.
Thus, the prior art fails to provide an adequate method of treating diseases associated with abnormal cellular proliferation, such as tumors/cancers.
There is thus a widely recognized need for, and it would be highly advantageous to have, a method devoid of the above limitation.